1. Field of the Invention
The present invention relates to a process for producing a catalyst capable of being used to produce olefin polymers with high crystallinity, and a process for producing such olefin polymers with this catalyst.
2. Description of the Prior Art
It is well known that olefin polymers with high crystallinity can be produced using the so-called Ziegler-Natta catalyst comprising a compound of a transition metal of Groups IV to VI of the Periodic Table and a metal of Groups I to III of the Periodic Table or an organo-compound thereof.
In the industrial production of olefin polymers, such as propylene polymers and butene-1 polymers, titanium trichloride compositions are particularly used as catalysts. In this process, however, amorphous polymers are produced as by-products in addition to olefin polymers with high stereo-regularity, the latter polymers being very valuable industrially.
Amorphous polymers have little industrial value and adversely affect to a great extent the mechanical properties of the processed products of olefin polymers, such as films, fibers and the like.
Further, the formation of the amorphous polymers uselessly consumes monomer starting material, and at the same time, equipment for removal of the amorphous polymers becomes necessary. This is a very serious disadvantage from an industrial point of view.
Consequently, it would be quite advantageous if the formation of such amorphous polymers could be completely or, at least, substantially inhibited.
Further, catalyst residues remain in the olefin polymers produced by this polymerization process and adversely affect the stability and processability of the polymers produced. Accordingly, equipment for removal of catalyst residues and for stabilization of the polymers becomes necessary.
These disadvantages in the polymerization process can be improved by increasing the catalytic activity which is expressed as the yield of olefin polymer per unit weight of catalyst. Thus, equipment for removal of the catalyst residues becomes unnecessary and, thus, a reduction in the manufacturing cost of the olefin polymer also becomes possible.
Titanium trichloride used for such purpose is obtained by (1) reducing titanium tetrachloride with hydrogen, followed by activation by powdering in a ball-mill, (2) reducing titanium tetrachloride with metallic aluminum, followed by activation by powdering in a ball-mill, and (3) reducing titanium tetrachloride with an organo-aluminum compound at -30.degree. C. to 30.degree. C. and heat-treating the resulting .beta.-type titanium trichloride at 120.degree. C. to 180.degree. C. to change the crystal form thereof.
However, none of the titanium trichloride catalysts thus-obtained is satisfactory in terms of the catalytic activity and the stereo-regularity of polymers produced therewith.
Further, other various processes for producing titanium trichloride have been proposed. For example, a process wherein .beta.-type titanium trichloride is treated with a complexing agent and then with titanium tetrachloride is disclosed in Japanese Patent Application (OPI) No. 34478/1972 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application"). Also, processes wherein titanium trichloride compositions obtained in the foregoing processes are treated with a complexing agent, or co-pulverized in a ball-mill, followed by washing with a solvent, are well known.
Further, processes for producing titanium trichloride by reduction of titanium tetrachloride with an organo-metallic compound in the presence of an electron-donating compound, such as an ether, are well known. For example, (1) a process comprising reducing titanium tetrachloride with an organo-magnesium or organo-aluminum compound in an ether medium, followed by ageing at 150.degree. C. to 200.degree. C. (e.g., as disclosed in Japanese Patent Publication No. 8768/1971), (2) a process comprising reducing titanium tetrachloride with an organo-aluminum compound at 160.degree. C. to 200.degree. C. in an ether solvent (e.g., as disclosed in U.S. Pat. No. 3,558,271), and (3) a process comprising reducing titanium tetrachloride with an organo-aluminum compound in an aromatic solvent in the presence of polyoxyethylene or polyoxypropylene, followed by heat-treating in the vicinity of the boiling point of the titanium tetrachloride (e.g., as disclosed in Japanese Patent Application (OPI) No. 27285/1972) are known. Also, processes for producing a solid titanium trichloride comprising treating titanium tetrachloride with an organo-aluminum compound in the presence of an ether to produce a liquid product, followed by heat-treatment at 150.degree. C. or less, are disclosed in Japanese Patent Application (OPI) Nos. 16298/1976, 76196/1976, 90998/1976, and 94496/1976.
Various processes for producing titanium trichloride catalysts with iodine or an iodine compound have been proposed. For example, processes wherein titanium trichloride is treated with iodine, bromine or an iodine or bromine compound are disclosed in Japanese Patent Application (OPI) Nos. 9178/1976, 81889/1976, and 117787/1976.
The present inventors proposed a process wherein titanium trichloride compositions are reacted with an ether compound in the presence of iodine or an iodine compound (Japanese Patent Application No. 108276/1976).
Also, a process wherein the liquid product, which is obtained by treating titanium tetrachloride with an organo-aluminum compound in the presence of an ether compound and iodine or an iodine compound, is contacted with a releasing agent (e.g., a Lewis acid) at 150.degree. C. or less to obtain a solid titanium trichloride is disclosed in Japanese Patent Application (OPI) No. 46598/1976. The description in Japanese Patent Application (OPI) No. 46598/1976 on the time the iodine or the iodine compound is added in the process is that such "is added prior to the reduction treatment, but, if in a substantial reduction term, it may be added after the reduction treatment is carried out. The term, substantial reduction term, means the time when the reduction of the titanium tetrachloride is not yet finished". Particularly, the following description "The effect of the present invention is not displayed even though iodine or an iodine compound is added after completion of the reduction" appears.